For the stability and commercial development of the perovskite solar cells (PVK-SCs), synthesizing high-efficiency dopant-free hole-transport materials (DF-HTMs) and exploring how the DF-HTM structure affects the photovoltaic performance is inevitable. Two small-molecule DF-HTMs based on 2,2′-bithiophene as a central part (denoted by BT-MTP and DFBT-MTP) were designed and synthesized. DFBT-MTP, with two more fluorine atoms substituted on the 2,2′-bithiophene group, exhibited enhanced photovoltaic property as DF-HTMs, including larger backbone planarity, declining highest occupied molecular orbit (HOMO) energy level, increasing hole transportation, more effective passivation, and efficient charge extraction. With fluorinated DFBT-MTP being applied as DF-HTMs in p–i–n PVK-SCs, an efficiency of 20.2% was achieved, showing ∼35% efficiency increase compared with the nonfluorinated BT-MTP-based devices. The leading power conversion efficiency (PCE) indicates that the fluorinated compounds should be a promising direction for exploring high-performance DF-HTMs in the p–i–n PVK-SCs.

Although several studies have explored green adsorbent synthesized from many types of agriculture waste, this study represents the first attempt to prepare an environmentally friendly rice bran/SnO2/Fe3O4-based absorbent with economic viability and material reusability, for the promotion of sustainable development. Here, rice bran/SnO2/Fe3O4 composites were successfully synthesized and applied for adsorption of reactive blue 4 (RB4) and crystal violet (CV) dyes in aqueous solutions. The adsorption data were well-fitted by the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacities of the RB4 and CV dyes as indicated by the Langmuir isotherm model were 218.82 and 159.24 mg/g, respectively. As results of response surface methodology (RSM) showed, the quadratic model was appropriate to predict the performance of RB4 dye removal. The findings exhibited that an optimum removal rate of 98% was achieved at 60 °C for pH 2.93 and adsorption time of 360 min. Comparative evaluation of different agricultural wastes indicated that the rice bran/SnO2/Fe3O4 composite appeared to be a highly promising material in terms of regeneration and reusability, and showed that the composite is a potential adsorbent for dye removal from aqueous solutions. Overall, the study results clearly suggest that an adsorbent synthesized from rice bran/SnO2/Fe3O4 magnetic particle composites provides encouraging adsorption capacity for practical applications for environmental prevention.

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Many researches report that the mobility in organic material is dependent on not only the gate field but also the grain size. There is also some evidence to prove that the gate length is strongly related to the carrier mobility. We construct both the analytical model of organic thin film transistor and the large signal circuit model designed by T-CAD to fit the measuredequations in both triode and saturation regions with mobility µ best fitted to measured I-V curves. The "best-fitted" µ increases with the gate length, and is related to the increase of total channel resistance due to the presence of small grains size of pentacene next to source/drain electrodes. We then use the Advanced Design System software to design the large signal circuit model. Similar to the MOSFET, we add the additional parameters to fit the DS DS V I − curves, ex: Rgd, Rgs, and Rp. Here, Rgd. With the circuit simulation, we find that Rgd presents the leakage current from gate to source, and it affects the slope of curves in the saturation region in the DS DS V I − curves. The equivalent circuit can fit the DS DS V I − curves very well with the proper parameter set.